A15628 | Hossam and Friends

Hossam makes a big party, and he will invite his friends to the party.

He has $n$ friends numbered from $1$ to $n$ . They will be arranged in a queue as follows: $1, 2, 3, \ldots, n$ .

Hossam has a list of $m$ pairs of his friends that don't know each other. Any pair not present in this list are friends.

A subsegment of the queue starting from the friend $a$ and ending at the friend $b$ is $[a, a + 1, a + 2, \ldots, b]$ . A subsegment of the queue is called good when all pairs of that segment are friends.

Hossam wants to know how many pairs $(a, b)$ there are ( $1 \le a \le b \le n$ ), such that the subsegment starting from the friend $a$ and ending at the friend $b$ is good.

The input consists of multiple test cases. The first line contains a single integer $t$ ( $1 \le t \le 2 \cdot 10^4$ ), the number of test cases. Description of the test cases follows.

The first line of each test case contains two integer numbers $n$ and $m$ ( $2 \le n \le 10^5$ , $0 \le m \le 10^5$ ) representing the number of friends and the number of pairs, respectively.

The $i$ -th of the next $m$ lines contains two integers $x_i$ and $y_i$ ( $1 \le x_i, y_i\le n$ , $x_i \neq y_i$ ) representing a pair of Hossam's friends that don't know each other.

Note that pairs can be repeated.

It is guaranteed that the sum of $n$ over all test cases does not exceed $10^5$ , and the sum of $m$ over all test cases does not exceed $10^5$ .

For each test case print an integer — the number of good subsegments.